The present invention is directed to electrical shift control devices for bicycle transmissions and, more particularly, to a method of using a motion sensor with a bicycle sprocket assembly.
Motion sensors are commonly used with bicycles to sense rotation of the wheel or pedal crank so that bicycle speed and cadence may be computed by a bicycle computer and displayed to the rider. Such information also may be used to control an automatic or semiautomatic bicycle transmission, wherein the bicycle speed or cadence may be used to determine when to change gear ratios. The typical motion sensor usually comprises a magnet attached to the wheel or crank arm and a magnetic sensor attached to the bicycle frame. When the magnet passes in close proximity to the magnetic sensor, the sensor provides a pulse to the bicycle computer. The speed or cadence then may be computed based on the elapsed time between successive pulses.